Pore characteristics of the formation exert significant control over both the development and enrichment of shale plays, as well as CO2 storage capacity of shale reservoirs. This research delved into the alteration of the Bakken shale's pore structure - a major target of underground CO2 storage under the PCOR partnership - when exposed to anhydrous and hydrous pyrolysis (AHP and HP) across a broad temperature spectrum (300-450 degrees C), aiming to uncover the influence of water in this process. First, N2 adsorption analysis was carried out, followed by the delineation and characterization of distinct pore families within the pore size distribution (PSD) curves of the samples. Subsequently, fractal dimension analysis was employed to gauge the intricacy of the pore structure. Next, generalized regression neural network (GRNN) and radial basis function (RBF) neural network were employed to model the N2 adsorbed/desorbed volume of pyrolyzates obtained from pyrolysis tests. Throughout the process of thermal maturity, AHP and HP pyrolyzates exhibited an overall rise in N2 adsorption capacity, BET surface area, meso-, macro-, and total pore volume. Conversely, the average pore diameter decreased. Also, HP pyrolyzates displayed notably higher N2 adsorption capacity compared to AHP pyrolyzates. Differences in total pore volume and surface area, attributed to mesopores and macropores, were evident between HP and AHP pyrolyzates across all temperatures, with HP pyrolyzates consistently displaying higher values for these pore characteristics. Five pore families akin to those in the original Bakken shale were found in AHP and HP pyrolyzates, displaying similar mean pore sizes. Although there were significant differences in elevation and magnitude, the pyrolyzates showed heightened peaks and increased volumetric representation compared to unheated shale. Overall, AHP and HP pyrolyzates exhibited a general decrease in pore surface complexity and roughness, while concurrently displaying heightened complexity within the pore network during thermal maturation. In the modeling section, the GRNN model demonstrated supremacy in estimating N2 volume adsorbed or desorbed, with an average absolute percent relative error (AAPRE) of 3.61% across the entire dataset. The subsequent sensitivity analysis underscored the significant impact of relative pressure and pyrolysis method on the output, emphasizing the significant contribution of water in shaping pore development throughout shale thermal evolution. This study can serve as a guideline for identifying areas in the Bakken Formation that are better suited for CO2 storage, considering factors such as thermal maturity , water satu- ration, given extensive availability of such data.

According to the practical characteristics of a mid-end signal controller, such as natural heat dissipation, outdoor installation, dustproof, waterproof and anticorrosive, a simple and compact cabinet of signal controller is designed. The size of the whole machine is about 600mm×400mm×1100mm, and the wall thickness of the cabinet is 1mm.The whole machine adopts natural heat dissipation of owning low cost, no power consumption and strong applicability, which is widely used in outdoor natural environment for cabinet heat dissipation. With the development of science and technology, outdoor information control equipment (especially traffic signal machine) becomes more and more precise, and its power density increases correspondingly, and its calorific value also increases relatively. In this case, the use of natural heat dissipation requires very high rationality of cabinet structure and layout. This paper based on SolidWorks Flow Simulation thermal Simulation software Simulation analysis and optimization of the simplified cabinet, and then provide a design reference for the research and development of the series of signal products

Fine reservoir characterization is the basis of tapping the potential of high-yield exploration and evaluation wells. In this paper, the comprehensive prediction of New 172-52 reservoir in high-yield exploration and evaluation well area is carried out by using seismic data combined with drilling data, the sand body in the study area is re-depicted, and the geological understanding after drilling is integrated. It is concluded that the effective thickness of the well area on the east side of the fault in this area changes rapidly and gradually becomes thicker to the southeast, and the sand body is developed and has good connectivity, and there is potential for edge expansion above the oil-water interface. In the well area on the west side of the fault, according to the seismic reservoir attribute, the abandoned well after drilling is at the edge of the sand body, and the sand body extends to the northeast around the well point, and meets the fault block at the high part of the structure, which has the potential of expanding the edge. Through fine reservoir characterization, the boundary and scale of sand bodies are explored, and the productivity potential of high-yield exploration and evaluation wells is tapped.

Coalbed methane (CBM) has been exploited in the deep area of the coal reservoir (>1000 m). The production of CBM vertical wells is low because of the high in situ stress, large buried depth, and low permeability of the coal reservoir. In this paper, efficient and advanced CBM development technology has been applied in the Libi Block of the Qinshui Basin. According to the characteristics of the coal reservoir in the Libi Block, the coiled tubing fracturing technology has been implemented in four cluster horizontal wells. Staged fracturing of horizontal wells can link more natural fracture networks. It could also expand the pressure drop range and control area of the single well. This fracturing technology has achieved good economic results in the Libi Block, with the maximum production of a single horizontal well being 25313 m(3)/d and the average single well production having increased by more than 60% from 5000 m(3)/d to 8000 m(3)/d. Based on the data regarding the bottom hole pressure, water production, and gas production, the production curves of four wells, namely, Z5P-01L, Z5P-02L, Z5P-03L, and Z5P-04L, were investigated. Furthermore, a production system with slow and stable depressurization was obtained. The bottom hole pressure drops too fast, which results in decreasing permeability and productivity. In this work, a special jet pump and an intelligent remote production control system for the CBM wells were developed; hence, a CBM production technology suitable for the Libi Block was established. The maximum release for the CBM well productivity was obtained, thus providing theoretical and technical support for CBM development with geological and engineering challenges.

In pyrite-bearing shaly sandstones, the distortion in the resistivity logging response of formations in high-frequency resistivity logging because of dispersion hinders the calculation of reservoir saturation. To eliminate the effect of resistivity dispersion of pyrite and shale, and to avoid factors, such as mineral composition, content, and distribution in natural cores, we synthesized twelve samples with dispersed pyrite and shale grains at high temperature and pressure (60 MPa and 120 °C). We performed experiments at different water salinities and oil saturations, and different frequency to assess the effect of frequency on the conductivity of pyrite-bearing shaly sandstones. Both the dispersed pyrite and shale grains show dispersion, and the real part of the complex resistivity decreases with increasing frequency. Based on symmetrical effective medium conductivity theory and the experimental data, the effective medium dispersion model for the real part of the complex resistivity for pyrite-bearing shaly sandstones is established considering the effect of pyrite and shale content on resistivity dispersion. Simulations suggest that the predicted resistivity dispersion by the model in pyrite-bearing shaly sandstones for variable frequency, and pyrite and shale content agrees with the experimental results. The proposed model can successfully predict the dispersion of pyrite-bearing shaly sandstones. Finally, the resistivity dispersion correction plot for the conductivity of pyrite and shale grains of 0.062 S/m and 0.031 S/m, respectively, is established based on the frequency applied to various electric logs, and the correction method for the high-frequency resistivity log response is given to obtain the real formation resistivity.

The conductance of pyrite-bearing laminated and dispersed shaly sands is not well understood and resistivity models for pyrite-bearing shaly sands are nonexistent. Thus, we first synthesize clean pyrite-matrix samples, and quartz-matrix samples with variable laminated shale, dispersed shale, and pyrite content and then perform petrophysics experiments to assess the effect of pyrite content on the conductivity of pyrite-bearing shaly sands. Second, based on the differences in conductivity and conduction pathways and geometries because of the variable composition of the pyrite-bearing laminated and dispersed shaly sands, we divide the shaly sands into their components, i.e., laminated shale, quartz grains, pyrite grains, hydrocarbon, dispersed shale, microscopic capillary water, and mobile water. A generalized resistivity model is proposed to describe the conductivity of pyrite-bearing laminated and dispersed shaly sands, based on the combined conductivity differential equation and generalized Archie equation. In the generalized resistivity model, the conductivity differential equation is used to describe the conductivity of dispersed inclusions in a host, whereas the generalized Archie equation is used to describe the conductivity of two conducting phases. Moreover, parallel conductance theory is used to describe the conductivity of dispersed shaly sands and laminated shale. Theoretical analysis suggests that the proposed model satisfies the physical constraints and the model and experimental results agree. The resistivity and resistivity index of shaly sands decrease with increasing conductivity and pyrite. Finally, the accuracy of the resistivity model is assessed based on experimental data from 46 synthetic core samples with different oil saturation. The model can describe the conductivity of clean pyrite-matrix samples, and quartz-matrix samples with different volumes of laminated shale, dispersed shale, and pyrite. An accurate saturation model of pyrite-bearing laminated and dispersed shaly sands is thus obtained and the log data interpretation in complex shaly sands can improve with the proposed model.

Tight sandstone reservoirs are characterized by complex pore structures and strong heterogeneity, and their seepage characteristics are much different from those of conventional sandstone reservoirs. In this paper, the tight sandstone reservoirs of Upper Jurassic Penglaizhen Fm in western Sichuan Basin were analyzed in terms of their pore structures by using the data about physical property, mercury injection and nuclear magnetic resonance (NMR) tests. Then, the seepage characteristics and the gas–water two-phase migration mechanisms and distribution of tight sandstone reservoirs with different types of pore structures in the process of hydrocarbon accumulation and development were simulated by combining the relative permeability experiment with the visual microscopic displacement model. It is shown that crotch-like viscous fingering occurs in the process of gas front advancing in reservoirs with different pore structures. The better the pore structure is, the lower the irreducible water saturation is; the higher the gas-phase relative permeability of irreducible water is, the more easily the gas reservoir can be developed. At the late stage of development, the residual gas is sealed in reservoirs in the forms of bypass, cutoff and dead end. In various reservoirs, the interference between gas and water is stronger, so gas and water tends to be produced simultaneously. The sealed gas may reduce the production rate of gas wells significantly, and the existence of water phase may reduce the gas permeability greatly; consequently, the water-bearing low-permeability tight sandstone gas reservoirs reveal serious water production, highly-difficult development and low-recovery percentage at the late stage, which have adverse impacts on the effective production and development of gas wells.

The fault-reservoir displacement pressure differential method, as a quantitative evaluation method of fault sealing which considering diagenetic time of fault rock, was improved based on the study of fault sealing mechanism and its influencing factors. A geology and mathematical model of quantitative evaluation of fault sealing considering diagenetic time was established. First, the depth of surrounding rock which has the same shale content and diagenetic degree as the fault rocks at the target was determined using the method of successive approximation at the given step length. Second, the displacement pressure of target fault rocks was calculated based on the relationship between the displacement pressure and the product of shale content and burial depth that was established for the study area. And third, the sealing states and capacity of the faults were quantitatively evaluated by comparing the calculated displacement pressure with that of the target reservoir. By the actual data of reservoirs at Banqiao Fault in Qikou sag and the result comparison between fault rock shale content method (SGR) and fault-reservoir displacement pressure differential method without considering the diagenetic time, it is verified that this method is more feasible and credible.

The major gas pay zones in the Middle Triassic Leikoupo Fm in the Sichuan Basin are Lei-1(the 1st member of the Leikoupo Fm),Lei-32(the 2nd interval of the 3rd member of the Leikoupo Fm) and Lei-43(the 3rd interval of the 4th member of the Leikoupo Fm).A set of dolomite reservoirs has been discovered in the Lei-33(the 3rd interval of the 3rd member of the Leikoupo Fm) in the western central Sichuan Basin in recent years.Their characteristics and distribution were studied by use of outcrop observation,core and logging data in combination with laboratory test results.The following understandings were obtained.a.These reservoirs are dominated by(gypsum-bearing) dolomicrite-silt-crystalline dolomite and grain dolomite,with inter-crystalline,inter-particle and intra-particle dissolution pores as the major pore types.Sabkha dolomitization and meteoric fresh water dissolution are the main factors leading to the formation of pores.b.The development and distribution of these reservoirs are mainly controlled by eustatic cycles and sedimentary facies belts and are most highly developed on the platform margins in the western and northwestern parts,fairly developed on the intra-platform shoal and tidal flat in the central part,and poorly developed in the intra-platform depressions.c.The reservoirs are so widely distributed in the western central Sichuan Basin and have such good oil/gas shows in the Moxi area of central Sichuan Basin that they might be the potential new gas pay zones in the Leikoupo Fm.

The major gas pay zones in the Middle Triassic Leikoupo Fm in the Sichuan Basin are Lei-1 (the 1st member of the Leikoupo Fm), Lei-32 (the 2nd interval of the 3rd member of the Leikoupo Fm) and Lei-43 (the 3rd interval of the 4th member of the Leikoupo Fm). A set of dolomite reservoirs has been discovered in the Lei-33 (the 3rd interval of the 3rd member of the Leikoupo Fm) in the western central Sichuan Basin in recent years. Their characteristics and distribution were studied by use of outcrop observation, core and logging data in combination with laboratory test results. The following understandings were obtained. a. These reservoirs are dominated by (gypsum-bearing) dolomicrite - silt-crystalline dolomite and grain dolomite, with inter-crystalline, inter-particle and intra-particle dissolution pores as the major pore types. Sabkha dolomitization and meteoric fresh water dissolution are the main factors leading to the formation of pores. b. The development and distribution of these reservoirs are mainly controlled by eustatic cycles and sedimentary facies belts and are most highly developed on the platform margins in the western and northwestern parts, fairly developed on the intra-platform shoal and tidal flat in the central part, and poorly developed in the intra-platform depressions. c. The reservoirs are so widely distributed in the western central Sichuan Basin and have such good oil/gas shows in the Moxi area of central Sichuan Basin that they might be the potential new gas pay zones in the Leikoupo Fm.